Acetylsalicylic acid

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Acetylsalicylic acid (Brand names: Aspirin, Aspro, Aspegic, Alka Seltzer, Aspirin Cardio, cardioaspirine, Cardiopirin, Cardipirin, among others) is a nonsteroidal antiinflammatory drug (NSAID) used for treating pain, fever, arthritis and other types of inflammation. Acetylsalicylic acid may also be used to reduce the risk of heart attack.




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Acetylsalicylic acid is a nonsteroidal antiinflammatory drug (NSAID) with analgesic, antipyretic and antirheumatic properties.

Acetylsalicylic acid inhibits irreversibly the enzyme, cyclooxygenase (COX), an early component of the arachidonic acid cascade, resulting in the reduced formation of prostaglandins and thromboxanes. Prostaglandins act as messenger molecules in the process of inflammation.

Low doses of Acetylsalicylic acid block platelet production of thromboxane A2 and thereby, platelet activation and aggregation. This property accounts for its use in the long-term prevention of heart attacks. The inhibitory effect of Acetylsalicylic acid on platelet thromboxane production persists for the lifespan of the platelet, around 7 to 10 days. As a result, acetylation of platelet cyclooxygenase and consequent inhibition of thromboxane formation is cumulative on repeated dosing.


  • Analgesic and Anti-inflammatory: pain–related conditions such as headache, dental pain, period pain, painful symptoms associated with colds (e.g. headache, sore throat, aching limbs)
  • Antipyrexia: fever
  • Anticoagulant:
    • prevention of thromboembolic disorders and cardiovascular events (Ischemic stroke, Transient ischemic attack (TIA), Prevention of recurrent MI, Unstable angina, Chronic stable angina)
    • Prevention of Complications of Pregnancy: Pregnancy-induced hypertension, Preeclampsia, Intrauterine growth retardation. Aspirin, is also used together with heparin in pregnant women with antiphospholipid syndrome, an autoimmune, hypercoagulable state caused by antiphospholipid antibodies. APS provokes blood clots as well as pregnancy-related complications such as miscarriage, stillbirth, preterm delivery, and severe preeclampsia.

[edit] DOSAGE

  • Mild to moderate pain:
    • Children 9-12 years: 400 mg at intervals of 4 to 8 hours if necessary, up to a maximum of 3 doses a day
    • Adolescents and adults: 400-800 mg at intervals of 4 to 8 hours if necessary, up to a maximum of 3 doses a day

  • For the prevention of cardiovascular disease:
Ischemic Stroke
and  Transient ischemic attack (TIA)
50 to 325 mg once daily Continue therapy indefinitely.
Prevention of Recurrent myocardial infarction 75 to 325 mg once daily Continue therapy indefinitely.
Unstable Angina Pectoris and Chronic Stable Angina Pectoris
75 to 325 mg once daily Continue therapy indefinitely.
Primary and Secondary Prevention of Cardiovascular Events in Patients with Type 1 or Type 2 Diabetes Mellitus
75 to 325 mg once daily Continue therapy indefinitely.
Coronary Artery Bypass 
325 mg once daily starting 6
hours post-procedure
Continue therapy for 1 year postprocedure
Percutaneous Transluminal 325 mg given 2 hours 160 to 325 mg once daily.
Coronary Angioplasty (PTCA) pre-angioplasty Continue therapy indefinitely.
Carotid Endarterectomy
80 mg once daily to 650
mg twice daily, started presurgery
Continue therapy indefinitely.

  • Prevention of Complications of Pregnancy (Pregnancy-induced hypertension, Preeclampsia, Intrauterine growth retardation, Pregnancy with existing conditions (e.g., SLE, positive cardiolipin antibody test): 80 mg daily from 13th to 26th weeks of gestation, or, as prescribed by a physician.


  • Patients with known allergy to NSAIDs.
  • Patients with the syndrome of asthma, rhinitis, and nasal polyps. Acetylsalicylic acid may cause severe urticaria, angioedema or bronchospasm.
  • Gastric or duodenal ulcers
  • Children or teenagers with viral infections because of the risk of Reye’s syndrome with concomitant use of Acetylsalicylic acid in certain viral illnesses.
  • Patients taking 15 mg or more methotrexate per week
  • During the last trimester of pregnancy


  • Avoid Acetylsalicylic acid in patients with severe renal failure (glomerular filtration rate less than 10 mL/minute)
  • Risk of Bleeding: The chance is higher in patients age 60 or older, have had stomach ulcers or bleeding problems, taking a blood thinning (anticoagulant) or steroid drug, taking other drugs containing prescription or nonprescription NSAIDs (Ibuprofen, Naproxen, or others), having 3 or more alcoholic drinks every day while using Acetylsalicylic acid or taking more or for longer than directed. Avoid Acetylsalicylic acid use one week prior to and during labor, delivery, and any surgical procedure because it can result in excessive blood loss.


  • Acetazolamide: Increased serum acetazolamide concentrations and toxicity due to competition at the renal tubule for secretion
  • Anticoagulant therapy (Heparin, Warfarin): Increased risk of bleeding because of drug-drug interactions and the effect on platelets
  • Anticonvulsants: Salicylate can displace protein-bound phenytoin and valproic acid, leading to decreased total concentration of phenytoin and increased serum valproic acid levels
  • Beta-blockers: Diminished hypotensive effects of beta-blockers due to inhibition of renal prostaglandins, leading to decreased renal blood flow, and salt and fluid retention
  • Diuretics: Diminished effectiveness of diuretics in patients with underlying renal or cardiovascular disease due to inhibition of renal prostaglandins, leading to decreased renal blood flow and salt and fluid retention
  • Methotrexate: Salicylate may inhibit renal clearance of methotrexate, leading to bone marrow toxicity, especially in the elderly or renal impaired
  • NSAIDs: Increased bleeding or may lead to decreased renal function
  • Oral hypoglycemics: Moderate doses of Acetylsalicylic acid may increase the effectiveness of oral hypoglycemic drugs, leading to hypoglycemia



Common: Gastrointestinal disorders such as heartburn, nausea, vomiting, abdominal pain

  • Uncommon: Hypersensitivity reactions such as skin reactions
  • Rare:
    • Severe bleedings such as cerebral bleeding, particularly in patients with non-stabilised hypertension and/or concomitant treatment with anticoagulants, which in isolated cases could be life-threatening
    • Gastrointestinal bleeding which in very rare cases can lead to iron deficiency anemia. Signs are black stools or vomit blood.
    • Gastrointestinal ulcers which in very rare cases can lead to perforation
    • Hypersensitivity reactions of the respiratory system ,gastrointestinal tract and of the cardiovascular system, particular in asthmatics. The following symptoms may occur: a drop in blood pressure, attacks of difficult breathing, rhinitis, nasal congestion, allergic shock, swelling of the face, tongue and larynx (angioedema)
    • Hypersensitivity reactions such severe skin reactions and up to severe feverish skin rash with mucosa involvement (erythema exsudativum multiforme)
    • Gastrointestinal inflammation
  • Very rare: Increased liver values
  • Frequency not known:
    • Hemolysis and hemolytic anemia in patients with severe forms of glucose-6-phosphate dehydrogenase (G6PD) deficiency have been reported
    • Renal impairment and acute renal failure
    • Bleeding, e.g. nosebleeds, bleeding gums, skin bleeding or urogenital bleedings, possibly with prolongation of the bleeding time. This effect can persist for 4 to 8 days after use
    • Headache, dizziness, impaired hearing ability; tinnitus and mental confusion can be signs of an overdose


These include dizziness, tinnitus, sweating, nausea, vomiting, and altered glucose metabolism, mental confusion, and hyperventilation, respiratory alkalosis, metabolic acidosis, and ketosis, fluid and electrolyte losses. Depression of the central nervous system may lead to coma, cardiovascular collapse and respiratory failure.
In children serious signs of over dosage may develop rapidly. In cases of over dosage, consult a doctor immediately.

Gastric lavage, forced alkaline diuresis, restoration of fluid, electrolyte and acid balance, dialysis and supportive therapy may be required.


The Effect of Aspirin on Clot Formation
Mechanism of action of Aspirin
NSAIDs: MOAs and Clinical Considerations



Non-steroidal anti-inflammatory drugs (NSAIDs)
Non-selective (COX-1 and COX-2 inhibitors) Aceclofenac   Acetylsalicylic acid   Benzydamine   Diclofenac   Flurbiprofen   Ibuprofen   Indometacin   Ketoprofen   Ketorolac   Ketorolac   Lornoxicam   Mefenamic acid   Morniflumate   Nabumetone   Naproxen   Niflumic acid   Piroxicam   Tenoxicam
Relatively COX-2 selective Meloxicam   Nimesulide
COX-2 selective inhibitors (Coxibs) Celecoxib   Etoricoxib   Parecoxib
Ophthalmic NSAIDs Bromfenac (ophthalmic)   Diclofenac (ophthalmic)   Flurbiprofen (ophthalmic)   Ketorolac (ophthalmic)   Nepafenac (ophthalmic)
Veterinary use Carprofen   Deracoxib   Firocoxib   Mavacoxib   Robenacoxib
Antimigraine preparations
5 HT1 agonists (Triptans) Almotriptan (Almogran, Axert)   Eletriptan (Relpax)   Frovatriptan (Frova, Migard, Menatriptan)   Rizatriptan (Maxalt)   Sumatriptan (Imigran)   Zolmitriptan (Zomig)
Ergot alkaloids Dihydroergotamine   Ergotamine
NSAIDs/ Analgesics Indometacin   Acetylsalicylic acid (Aspirin)   Diclofenac (Voltaren)   Ibuprofen (Advil, Brufen, Dolgit, Nurofen)   Ketorolac (Toradol)   Naproxen (Naprosyn, Aleve)   Nimesulide   Paracetamol (Efferalgan, Panadol...)
Prophylaxis Cinnarizine (Stugeron, Stugeron forte)   Flunarizine (Sibelium)   Nifedipine (Adalat)   Pizotifen   Propranolol (Inderal)   Topiramate (Topamax)